The present invention relates to a floating-point data operating unit, perticularly to a unit for operating on a floating-point number expressed in a floating-point representation having a variable-length exponent part.
A floating-point representation is a number system often used for a scientific calculation because it makes it possible to manipulate large numbers as well as small numbers with a high precision.
FIG. 1 illustrates a typical example of data expressed in the conventional floating-point representation.
According to FIG. 1, reference numeral 1 indicates a bit representing the sign information of a numerical value i.e. the sign information of a mantissa, reference numeral 2 indicates a bit representing the sign information of an exponent, and reference numeral 4 indicates the absolute value information of the exponent; portions indicated by reference numerals 2 and 4 are collectively referred to as an exponent part. Reference numeral 5 indicates the mantissa part and reference numeral 6 represents the boundary between the exponent part and the mantissa part.
In the conventional floating-point representation, the boundary 6 between the exponent and mantissa parts is fixed, thus the number of bits for representing the exponent is constant, which leads to a drawback that the range of values that can be represented is limited. Furthermore, even if there are unused bits because the value of the exponent part is small, such free bits cannot be used for other purposes. This means that the conventional floating-point representation is not flexible enough, for example, to utilize the unused space of the exponent part to improve the precision of the mantissa part.